The Collaborative International Dictionary of English v.0.48:

Howlet \Howl"et\, n. [Equiv. to owlet, influenced by howl: cf.
   F. hulotte, OHG. h?wela, hiuwela.] (Zool.)
   An owl; an owlet. [Written also houlet.] --R. Browning.
   [1913 Webster]